英语达人 帮我分析一个句子some discrepancies have been described between the results of studies performed with a patent-protected formulation of glucosamine sulfate distributed as a drug and those having used glucosamine preparations purchased from global suppliers,packaged and sold over the counter as nutritional supplements.最后一个逗号后面的句子到底是哪个的定语 是those 还是glucosamine preparations的
问题描述：
英语达人 帮我分析一个句子
some discrepancies have been described between the results of studies performed with a patent-protected formulation of glucosamine sulfate distributed as a drug and those having used glucosamine preparations purchased from global suppliers,packaged and sold over the counter as nutritional supplements.最后一个逗号后面的句子到底是哪个的定语 是those 还是glucosamine preparations的
答
glucosamine preparations
答
是glucosamine preparations，因为those having used 也是glucosamine preparations的定语
答
这个句子难以从语法上判别,只能从逻辑上分析.
从定语packaged and sold over the counter as nutritional supplements.看,它修饰的是实物名词,因为只有实物才可以“包装、在柜台销售”（packaged and sold over the counter）,所以修饰对象之能是：drug and those这两个词.这个定语应该对those的补充修饰.